Known apparatus for controlling the above-mentioned process includes either a programmable or hard wired computer. Such systems are known from German Patent DE-PS No. 2 504 843, and German Patent Publications DE-AS No. 2 539 113 and DE-OS No. 2 655 948 (to which U.S. Pat. Nos. 4,063,539, 4,099,495, and 4,174,688 correspond). Since such computers consist of many components and may have a relatively complicated structure, a multiplicity of errors can occur. For this reason, an auxiliary, redundant control system is provided which operates only upon malfunction of the main computer. Generally, such an auxiliary control system is sufficient only to allow the operation of the internal combustion engine until such time as the next repair location can be reached.
In the known system, monitoring signals are furnished periodically by the program as it is being executed. These monitoring signals are monitored by an error detecting circuit. The auxiliary computing apparatus is switched in only if there is an error in the program as signified by a lack of monitoring signals. However the possibility exists that no control signals are applied to the cyclically operative apparatus by the main computer even though its program seems correctly operative. Further, in the known system, no error is detected if the program proceeds correctly, but not in proper synchronism to reference mark signals which are being received for timing the cyclical operation.